A great resource for stuff like this is gun-deals.com, where you can search major distributors by parameters like case material, primer type, primer corrosiveness, etc, and it will give you cost per round, even including shipping. Best I see on there is 232.50 plus shipping for a case of 500 Prvi Partizan.
I bought some 7.62x39 brass several years ago from a seller on TFL and while packing the order, the seller noticed he had both large and small primer brass. So, be aware of this potential issue. The brass he had was a mix of American and European manufacturers.
